Tektronix Phaser 740, Service Manual

Page: 75 / 148

Service Guide
63
Light, faded, pale prints
1.
The imaging unit is old or has been
exposed to too much room light.
Replace the imaging unit.
2. Is the paper in good condition and
appropriate for a laser printer?
3.
Is the printer printing within its
environmental specifications? For
the Phaser 750 printer, print the
built-in Diagnostic Test Page; the
current temperature and humidity
is printed on the page.
4. Check the media type and tray type
for proper match. If printing is
weak on paper only, the printer
may be printing in transparency
mode. Does the media in the multi-
purpose feeder match the default
setting made using the front panel?
Check to see if paper was picked
from a transparency tray or if the
multi-purpose tray is set for
Transparency.
5.
For desired paper, run the front panel routine Calibrate for Paper.
6. Check to see if the Color Calibration menu is set to print lighter.
7. The high-voltage board is not outputting sufficient voltage to the second bias
transfer roller, causing poor transfer of toner to paper. Likewise, low voltage to
the toner cartridge will cause insufficient transfer of toner to the
photoconductive belt.
8. Inspect the high voltage connector for poor contact with the second bias transfer
roller.
9.
The beam from the laser scanner is weak and is not properly exposing the
photoconductive belt. Poor laser exposure results in the negative charges
remaining on the photoconductive belt instead of being “erased” by the laser
beam, thereby retarding toner transfer from the toner cartridges. Replace the
laser scanner.
10.
Inspect the path the laser beam travels for contamination.
11.
Inspect the action of the cartridge selector to ensure that it is pushing the toner
cartridges into full contact with the photoconductive drum.
12. Replace the imaging unit.
13.
Replace the second bias transfer roller.
14.
Replace the engine control board.
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